Process for metalation

ABSTRACT

POLYMERS AND COPOLYMERS OF CONJUGATED DIENES (BUTADIENE, ISOPRENE, ETC.) AND COPOLYMERS OF SUCH A CONJUGATED DIENE WITH A VINYL AROMATIC HYDROCARBON (STYRENE, ETC.) ARE METALATED WITH AN ALKYL KITHIUM, E.G. BUTYLITHIUM, TOGETHER WITH POTASSIUM HYDROXIDE OR POTASSIUM OXIDE OR A POTASSIUM SALT OF AN INORGANIC ACID.

Dec. 25, 1973 A, HALASA ETAL 3,781,263

PROCESS FOR METALAT'ION Filed July 13, 1972 3,781,263 PROCESS FOR METALATION Adel F. Halasa, Bath, and George B. Mitchell, Canton, Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio Filed July 13, 1972, Ser. No. 271,474 Int. Cl. C0811 5/02 US. Cl. 260--94.7 A 4 Claims ABSTRACT OF THE DISCLOSURE Polymers and copolymers of conjugated dienes (butadiene, isoprene, etc.) and copolymers of such a conjugated diene with a vinyl aromatic hydrocarbon (styrene, etc.) are metalated with an alkyl lithium, e.g. butyllithium, together with potassium hydroxide or potassium oxide or a potassium salt of an inorganic acid.

The invention relates to a novel method of metalating rubber homopolymers and copolymers of conjugated dienes containing 4 to 6' carbon atoms, and copolymers of one or more such conjugated dienes with one or more vinyl aromatic monomers. The copolymers that are treated may be either random copolymers or block copolymers. The metalated products may be used where other metalated polymers have been used, as in the production of hydrocarbons by reaction with a metal halide, and they may have other uses.

The metalation of such rubbers with butyllithium and a polar compound, e.g. an ether or amine, etc. is disclosed in Naylor 3,492,369. The use of 1) an organolithium compound and (2 a selected organic compound of sodium, potassium, rubidium or cesium as a polymerization initiator is disclosed in Wofrord 3,294,768.

In the metalation ,of rubbers by known procedures, the rubber is-depolymerized as evidenced, for instance, by loss of resistance 'to cold flow and loss in molecular weight. Such loss is prevented or reduced by using a mixture of (1) alkyllithium (preferably n-butyllithium) and (2) potassium hydroxide, oxide, a halide or phosphate. Thus, for each 100 parts by Weight of polymer there are used: 0.001 to 2 parts (and preferably 0.002 to 0.2 part) of lithium as alkyllithium which contains 4 to 8 carbon atoms; 0.01 to 20 parts (and preferably 0.1 to 10 parts) of KOH, K 0, KCl or K PO The metalated polymers and copolymers are useful for the production of graft copolymers, and for this purpose it is immaterial whether lithium or potassium or a mixture of these metals constitutes the metal of the metalated rubber. The grafts can be formed by reacting the metalated polymer or copolymer of this invention with an alkyl halide. (in which the alkyl group contains 4 to 8 or more carbon atoms) or a monomer (e.g. a conjugated diene such as butadiene, isoprene, etc. or other aliphatic hydrocarbon monomers, e.g. ethylene, propylene, isobutylene, etc. or a vinyl aromaticmonomer, e.g. styrene, alpha-methylstyrene, etc. or other polar monomers, e.g. acryslonitrile, methylarylate, vinyl ethers, vinyl sulfones, etc.

The metalation is carried out at any usual metalating temperature such as to 150 C. A preferred temperature range is 25 to 60 C. The solvent used is a solvent such as a hydrocarbon aliphatic solvent, usually employed in the polymerization of monomers'in the production of rubber using butyllithium as the catalyst. Such solvents are saturated parafiinic hydrocarbons or aliphatic cyclo hydrocarbons containing to 10 carbon atoms. The potassium co-metalating agent may be dispersed in such a hydrocarbon or it may be dispersed in a mineral oil.

It has been recognized that rubber polymers lose molecular weight duringthe known metalation reactions. See, for instance, Metalation of Unsaturated Polymers United States Patent 0 and Formation of Graft Polymers, by authors which include one of the co-inventors, published in the Journal of Polymer Science, Part A-l, vol. 9, pages 139-45 (1971). On page 142 there is a table which shows that during metalation there is loss in the molecular weight of polybutadiene and polyisoprene with resultant decrease in intrinsic viscosity. The article refers to low metalation. levels, but there is also a loss in molecular weight with higher metalation levels. When potassium hydroxide or other potassium compound to which the invention relates is used along with butyllithium, the polymers and copolymers are not degraded, and no objectionable gel is formed. The microstructure of the resulting grafted copolymer is typical of diene polymerization initiated by alkyllithium in a hydrocarbon solvent. However, these grafted copolymers because they are branched and therefore have a broad molecular weight distribution, have the advantage of less cold flow, better processability and better wear wet-traction properties characteristic of graft copolymers. They are useful in the manufacture of tires and other rubber goods.

EXAMPLE 1 In producing the graft copolymer of this example, three samples of butadiene were polymerized, the polymers were metalated, and then the metalated polymers were treated with butadiene to produce the graft copolymer. The processes were substantially identical, the differences being indicated in the following table which refers to the steps by which the three graft copolymers were produced and gives the properties of the three products. In the table, BD stands for butadiene, n-BuLi stands for n-butyllithium, and t-BuLi stands for t-butyllithium. For the polymerization, other alkyllithiums may be used including alkyls with 4 to 8 carbon atoms. For the metalation, an active alkyllithium is required in which the lithium is in the secondary or tertiary position, if the alkyl group is butyl. In the metalation and grafting steps, additional heptane is sometimes used to dilute the reaction mixture because in the formula given for the polymerization a viscous product was often obtained which is difficult to handle in the subsequent steps of the operation. Ex ample 3 illustrates the addition of heptane to the polymerization reaction mixture. In indicating the properties of the polymer and the graft, DSV stands for dilute solution viscosity, and IR stands for infra red analysis.

TABLE I Run A B C Polymerization:

Blend:

Butadiene, g 168 168 168 Heptane, g 632 632 632 n-BuLi, mm./ b./d 0.6 0. 6 0. 6 Temperature, C.. 60 60 60 Time, hours 4 4 5. 5 Properties of polymer:

DSV 2. 09 2. 39 2. 57 0 0 0 37. 2 37. 5 39. 1 52.1 8. 8 Metalation:

Heptane added, g 700 700 700 Metalating agent: t-BuLi, mmol./l00 g. pol 6. 0 6. 0 6. 0 KOH, mmo1./100 g. 1301.... 6. 6 6. 6 6. 6 Temperature, C 55 55 55 Time, hours 16 16 16 Gragtiing dd 6 ep ane a e 300 0 0 Blend: g

Butadiene, g 112 112 .112 Heptane, g 428 428 428 Temperature, C. 50 55 55 Time, hours 4. 6 3 3. 5 Properties of graft copolyme DSV 3. 81 3. 57 0 0 DSV3.54 Percent Gel- T,* -97 c. ML/4/212 F.175 IR:

cis-1,4%36.2 trans-1,4%54.8 1,2%-9.0

*T stands for glass transition temperature.

EXAMPLE 2 The mixture of grafts was then compounded according to the following recipe:

Parts by weight {Polymer 100 ISAF Black 70 Oil 43 Zinc oxide 2.5 Stearic acid 2.0 Antioxidant 1,0 Sulfur 1.7 Accelerator 1.4

The polymer was vulcanized at 300 F. and tests were made on samples vulcanized at this temperature for the times indicated. The properties of the vulcanizate are recorded in the following table.

TABLE II ML/4/2l2" F. --l64 Tensile strength (23 cure) -1625 p.s.i. Ultimate elongation (23' cure) --250% Steel ball rebound (35 cure): 3

at 73 F.49% at 212 F.60% Youngs modulus index: 4

at 10,000 p.s.i. 70 C.

ASTM and literature references:

.ASTM Designation D1646-68, 2 ASTM Designation D412-68. Dillon, .T. H., Prettyman, I. 3., Hall, G. L. J. Appl.

Phys. 15, 309 (1944). ASTM Designation D797-64.

EXAMPLE 3 Four other polybutadienes were produced by the procedure indicated in Table H, and these were metalated and graft copolymers were produced. In producing the graft, only 35 parts of butadiene (BD) was grafted onto 100 parts by weight of metalated polybutadiene backbone. The details of the procedures are given in the following table.

TAB LE III-continued R1111 D E F G Temperature, C 50 50 50 50 Time, hours 18 M 24 16 Grafting:

Blend:

1 (3 hours at 60 C.) (16 hours at 50 0.3. i (6 hours at 60 C.) (17 hours at 46 C.

Substantially equal amounts of graft polymer produced in the four diiferent runs were blended on a cold mill and the properties of this graft copolymer are given in the following table.

DSV1.55 Percent gel0 T 98 C. ML/4/2l2 F.--27 IR:

cis-l,4%-35.6 trans-1,4%55.7 1,2%-8.7 *See Example 1,

EXAMPLE 4 The mixture of graft polymers was then blended according to the foregoing recipe and on curing at 300 F. a vulcanizate was obtained which had the following properties:

TABLE IV ML/4/2l2 F. -36 Tensile strength (23'cure) 1875 p.s.i. Ultimate elongation, percent (23' cure) 1-470 Steel ball rebound (35 cure) at 73 F.40% at 212 F.49%

Youngs modulus index at 10,000 p.s.i. C.

1 See Table II.

EXAMPLE 5 Butadiene prepared in substantially the same manner as in the preceding examples was metalated with t-butyllithium and potassium hydroxide in much the same manner as the preceding examples, except exactly twice as much of the metalating agents was employed at substantially the same temperature-between 50 and 60 C.- until the metalation reaction was complete.

Styrene was grafted on to the metalated polybutadiene by adding 25 parts of styrene per each 100 parts of the metalated polybutadiene backbone at 50 C. for 2 hours. The properties of the graft copolymer are given in the following table:

TABLE V DSV-LSS' Percent gel-0 ML/4/212" F.l26 T,; 97 C. IR:

cis-1,4%30.6 trans-l,4%42.8 1,2%6.2 Styrene, percent- 20.3

Other backbone polymers may be produced from other monomers as above indicated, and these may be metalated with KOH, K 0, KCl or K PO to produce metalated backbones which may be reacted with a conjugated diene, an alkyl halide, an aliphatic hydrocarbon monomer, a vinyl aromatic monomer, or a polar monomer within sub- 5 6 stantially the same temperature range above indicated 3. The process of claim 1 in which the metalation to produce other products for use in tires or mechanical temperature is 25 to 60 C. goods, etc. 4. The process of claim 1 in which the modifier is We claim: potassium hydroxide. 1. The process of metalating a homopolymer of a 5 conjugated diene containing 4 to 6 carbon atoms or a References Cited copolymer of such a diene and a vinyl aromatic monomer, FOREIGN PATENTS which process comprises reacting at 0 to 150 C. in a 873,656 7/1961 Great Britain 26094.2 hydrocarbon aliphatic solvent, 100 parts of the homo 1,478,225 3/1967 France 260 877 X polymer or copolymer with 0.001 to 2 parts of a second- 10 ary or tertiary alkyllithium which contains 4 to 8 carbon 1144151 3/1969 Great Bmam 260*877 X f Pam i a 3 class JOSEPH L. SCHOFER, Primary Examiner consisting of potassium hydroxide, potassium oxide and potassium salts of an inorganic acid of the class consisting HAMROCK, Asslstant EXamlnel of the halides and the phosphates. 5

2. The process of claim 1 in which polybutadiene is metalated. 26085.l, 94.7 HA

my UNITED STA'IES PATENT OFFICE CERTIFICATE OF CORRECTION December 25, 1975 Patent. No- 5 ,784 265 Dated Invencofls) Adel F. Halasa and George B. Mitchell It is certified that error appears in the and that said Letters Patent are hereby corrects above-identified patent d as shown below:

. Column 2, Line 52 (in Table I) "b'./d. should read I Column 5,- Line e5.,('in Table 111'), "b./ 1" should. read Signed and sealed this lth day of April 19%;.

(SEAL) v Attest: o EDWARD M.FLETGH,ER,,JR. I o. MARSHALL DANN y Atte sting Officer Commissioner of Patents 

